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Miaphysitism, sometimes called henophysitism, is Cyril of Alexandria's Christological formula holding that in the person of Jesus Christ, divine nature and human nature are united (heis, "one" or "unity"; feminine nominative singular: mia; stem: , hen) in a compound nature ("physis"), the two being united without separation, without mixture, without confusion and without alteration.
Historically, Chalcedonian Christians have considered miaphysitism in general to be amenable to an orthodox interpretation, in contrast to monophysitism. From 431 on, Oriental Orthodoxy uses the term "Miaphysite" for themselves but prefer to call themselves non-Chalcedonians.
The term "miaphysitism" arose as a response to Dyophysite criticisms of monophysitism. As Nestorianism had its roots in the Antiochene tradition and was opposed by the Alexandrian tradition, Christians in Syria and Egypt who wanted to distance themselves from the extremes of Nestorianism and wished to uphold the integrity of their theological position adopted this term Miaphysite to express their position.
The theology of miaphysitism is based on an understanding of the nature (Ancient Greek: , physis) of Christ: divine and human. After steering between the doctrines of docetism (that Christ only appeared to be human) and adoptionism (that Christ was a man chosen by God), the Church began to explore the mystery of Christ's nature further. Two positions in particular caused controversy:
In response to Eutychianism, the latter Council adopted dyophysitism, which clearly distinguished between person and nature, stating that Christ is one person in two natures, but emphasizes that the natures are "without confusion, without change, without division, without separation".
The Monophysites rejected this definition as verging on Nestorianism and instead adhered to a wording of Cyril of Alexandria, the chief opponent of Nestorianism, who had spoken of the "one (mia) nature of the Word of God incarnate" ( ? mía phýsis toû theoû lógou sesark?mén?) but they failed to see that the less emphatic feminine form mia means "one, unity", whereas the emphatic masculine form mono- means "only, alone" without a sense of unity. The distinction of this stance was that the incarnate Christ has one nature, but that nature is still of both a divine character and a human character, and retains all the characteristics of both.
The Council of Chalcedon (451) was often seen as a watershed for Christology among the Chalcedonians as it adopted dyophysitism. However, as Oriental Churches, especially the Copts in Egypt, who held to Miaphysitism, rejected the decision, the controversy became a major socio-political problem for the Eastern Roman Empire. There were numerous attempts at reunion between the two camps (including the Henoticon in 482), and the balance of power shifted several times. However, the decision at Chalcedon remains the official teaching of the Eastern Orthodox Church, the Catholic Church and traditional Protestants. The non-Chalcedonian Orthodox Churches are usually grouped together as Oriental Orthodox. Over recent decades, leaders of the various branches of the Church have spoken about the differences between their respective christologies as not being as extreme as was traditionally held.
John Meyendorff, a historian of this period of Church history, held that the official teaching of the Eastern Orthodox Church is not expressed by Chalcedon alone, but by "Chalcedon plus Cyril" - i.e., the dyophysite position expressed by Chalcedon, plus Cyril's miaphysite expression quoted above in its Orthodox interpretation - with the former attempting to express the inexpressible from one side (the dyophysite side) and the latter doing the same from the miaphysite side, both approaches being necessary and neither sufficient by itself.
Much has been said about the difficulties in understanding the Greek technical terms used in these controversies. The main words are ousia (, "substance"), physis (, "nature"), hypostasis (, "being"), and prosopon (, "person"). Even in Greek, their meanings can overlap somewhat. These difficulties became even more exaggerated when these technical terms were translated into other languages. In Syriac, physis was translated as ky?nâ (?) and hypostasis was qnômâ (). However, in the Church of the East, which followed the East Syriac rite, qnômâ was taken to mean nature, thereby confounding the issue further. The shades of meaning are even more blurred between these words, and they could not be used in such a philosophical way as their Greek counterparts.
The Miaphysite Churches (or "Oriental Orthodox Churches"), all in communion with each other are :